Quality Control Rad T 110

Aim : The purpose of QC to achieve high quality images with the least amount of radiation. Quality Control is a part of Quality Assurance program

Test Types: Acceptance test Monitoring test Annual Test After repair or tube replacement

Acceptance Test: Performed upon newly installed equipment to verify purchase specification and to establish performance base line. Frequency: To be performed once only when new machine is installed

Monitoring Test: Performed for vital parameter on routine basis. Frequency: Every 2-3 months

Annual Test: Performed for vital parameter Frequency: once a year

Parameters to be checked Beam Alignment and Collimator Accuracy Radiation output and linearity of mR/mAs versus kV (Large and small FS Assessment of Total Beam Filtration (HVL) Assessment of Focal Spot size Accuracy and constancy of Exposure Timer Measuring of Scattered Radiation (using Water Phantom) Leakage Radiation from X-Ray tube 1-5 Monitoring test, 2- Annual Test

Parameters to be checked 1. Beam Alignment and Collimator Accuracy Small hole Beam Alignment Test Tool

Parameters to be checked 1. Beam Alignment and Collimator Accuracy X-ray Tube Radiation beam Light beam Test Tool

1. Beam Alignment and Collimator Accuracy Improper central ray alignment will distort a radiographic image. When used with the Collimator Test Tool, this device provides a simple means of determining if the X-ray beam is perpendicular to the image receptor and centered with respect to the light field.

1. Beam Alignment and Collimator Accuracy

Parameters to be checked 2. Constancy of Radiation output and linearity of mR/mAs versus kV2 (Small & Large focus) Victoreen Kv Meter Displays kVp maximum, kVp average, kVp effective, dose and time

Parameters to be checked Constancy of Radiation output and linearity of mR/mAs versus kV2 (Small & Large focus) Set mAs=20 for LF & 10 for SF X-ray Tube Radiation beam Measure kVp & Output Table top

Radiation output and linearity of mR/mAs versus kV The mR/mAs relationship must be linear and acceptable kVp measured by the kV Meter must be within the acceptable range ( i.e. + 10% of kVp indicated by machine) The exposure dose (Output) must be within acceptable limits .

Parameters to be checked 3. Assessment of Total Beam Filtration / (HVL) HVL(Half Value Layer): is the most frequently used factor for describing both the penetrating ability and the penetration through specific objects. Defined: thickness of material penetrated by one half of the radiation Unit: mm or cm Filtration: attenuation of photon according to their Energy ( simply the ability to get rid of unnecessary radiation)

Parameters to be checked 3. Assessment of Total Beam Filtration (HVL)

Parameters to be checked 3. Assessment of Total Beam Filtration (HVL) X-ray Tube Put Aluminum Shield with different thickness 1,2,3,4 mm Measure Output only Table top

Parameters to be checked 3. Assessment of Total Beam Filtration (HVL) HVL=3.0 mm (acceptable limit > 2.5 mm Al)

Parameters to be checked 4. Assessment of Focal Spot size Focal Spot area: is the surface area of the anode that is bombarded by electron beam. For Radiography units from 0.6 to 2.0 mm For Mammo units 0.3 –to 0.6

Parameters to be checked 4. Assessment of Focal Spot size Fine Parallel line Focal Spot Test Tool

Parameters to be checked 4. Assessment of Focal Spot size Focal Spot Area( level) X-ray Tube Test Tool 60 cm from the tube Low Speed film Couch

Parameters to be checked 4. Assessment of Focal Spot size A small focal spot size is used to obtain x-ray image with minimum blur. Small focal spot tend to concentrates heat and gives load on focal spot area. If the quantity of heat delivered during an individual exposure exceeds the track capacity, the anode surface can melt.

Parameters to be checked 4. Assessment of Focal Spot size so … it is necessary to measure the focal spot size and compare it with the original focal spot size with the machine. Focal spot size of any machine is written on the top of X-ray Tube.

Parameters to be checked 4. Assessment of Focal Spot size

Parameters to be checked 5. Accuracy and constancy of Exposure Timer X-ray Tube Measure the time compare it with time of exposure from the machine Table top

Parameters to be checked 6. Measuring of Scattered Radiation (using Water Phantom) When x-ray beam or gamma radiation passes through an object it can either Penetrate the object without interacting It can interact with matter and be completely absorbed. It can interact and scattered or deflected from original direction.

Parameters to be checked 6. Measuring of Scattered Radiation (using Water Phantom) X-ray Chest Bucky X-ray Tube Water or Chest Phantom Ionization chamber Ionization Chamber 1 m from center

Parameters to be checked 7. Leakage Radiation from X-Ray tube Rarely done. Typically for very old units. To test if there is any leakage of radiation from the x-ray tube.

Parameters to be checked Fluoroscopic Unhappiness and spatial Resolution The test pattern should be placed on the input window of the II and oriented so that the bar patterns are imaged perpendicular to the raster lines of the monitor display.

MONITOR ISSUES: QUESTIONS ASKED CRT vs. LCD LCD How many Mpx 5 What about the contrast ratio? 250+ How many bits 8,10, or 16? 9-10 Monochrome LCD or color LCD? Color Courtesy of E. Samei 56

Consumer grade or medical grade display Medical What about PDAs? Do NOT Use What about ambient conditions Modest Do displays need testing? Yes

Luminance Viewboxes • Low intensity: – 1000-2000 nits (cd/m2) • High intensity: – 2000-3000 nits (cd/m2) • Mammo: – 3500-5000 nits (cd/m2) Monitors ~ 75-600 nits (cd/m2)

LCD VS CRT DISPLAYS Barco

Monitor QC • Luminance calibration􀃎 Photometer • Focus (sharpness) 􀃎 test patterns • Test Patterns – SMPTE (Society of Motion Picture & Television Engineers) – AAPM TG18

Materials Required: Hardware: densitometer “puck” for correct monitor (CRT, LCD, BW, Color) USB expander memory stick Software: testing software compatible to CPU operating system (e.g.Win XP), and to manufacturers software

Viewing Conditions Illuminance Direct Sunlight = 105 lux Overcast = 103 lux Twilight = 101 lux Moonlight = 10-1 lux Office = 75 100 lux Reading room = 2 -25 lux • Ambient Light – Reflected • specular & diffuse – Decreases image contrast – Anti-reflective coating • Reduces luminance – CRT worse than LCD

Monitor Testing The acquisition workstation and secondary displays should be tested frequently using a standard image test pattern. The SMPTE RP-133 (Society of Motion Picture and Television Engineers) or AAPM TG-18 QC test patterns are suitable.

Using the SMPTE Test Pattern There should be no blurring or bleeding of bright display areas into dark areas or aliasing of the spatial imaging patterns. All monitors used for interpretation should be tested at least monthly

Using the SMPTE Test Pattern For the dynamic range test, both the 5% and 95% contrast areas should be visible and distinctly different than the adjacent 0% and 100% areas. Therefore:

Spatial Resolution & Aliasing The spatial resolution (linearity) and aliasing (distortion) of the monitor are within acceptable limits if the high contrast bar patterns in the test image are distinct as simple black and white pairs.